Less than a week after announcing the deployment of additional US personnel to Iraq, the White House has said that up to 300 more troops are being sent to the country to bolster security at key facilities amid an organized push by ISIS militants.

In a letter to Congress on Monday, President Obama wrote that additional troop deployments are “a prudent measure to protect US citizens and property.”

“This force is deploying for the purpose of protecting U.S. citizens and property, if necessary, and is equipped for combat,” wrote the President.

The letter, the third in two weeks, outlined that the additional force would include a detachment of helicopters as well as unmanned aerial vehicles, or drones. The troops are meant to reinforce security at US diplomatic facilities, as well as Baghdad International Airport.

Taking into account Monday’s announcement by the administration, recent US reinforcements into Iraq now stand at 875. On June 16, the president authorized a 275 troop deployment to strengthen embassy security in Baghdad.

The White House also authorized 300 troops to travel to Iraq in an advisory role, to train and assist Iraqi forces against ISIS following an embarrassing withdrawal from Mosul earlier in June. The withdrawal brought into sharp focus the level of combat readiness of Iraq’s armed forces.

On Monday, ISIS (the Islamic State of Iraq and the Levant, or simply Islamic State) announced the creation of a caliphate, or an Islamic state governed by Sharia law, throughout its controlled territory within Iraq and Syria. The group proclaimed its leader, Abu Bakr al-Baghdadi, as the caliph and demanded Muslims around the world pledge their allegiance.

As ISIS has expanded its reach within Iraq, questions regarding Baghdad’s security have been raised. Though State Department spokesperson Jen Psaki said the US embassy in the city “remains open and will continue to engage daily with Iraqis and their elected leaders,” officials cited by the Washington Post believed the additional troop deployments were aimed at not only protecting the embassy, but also ensuring escape routes in the event of an evacuation.